class MyNumbers:
      def __iter__(self):
            self.a = 1
            return self
      
      def __next__(self):
            if self.a <= 20:
                  x = self.a
                  self.a += 1
                  return x
            else:
                  raise StopIteration
            
myclass = MyNumbers()
myiter = iter(myclass)

for x in myiter:
      print(x)